Add check for valid UTF-8 post decoding

[CathalMullan]

Trying to minimize cost of UTF-8 checks. Can we do the single UTF-8 check upfront, and then not need to do any checks during parameter extraction?

EDIT: Looks like simdutf8 didn't boost performance locally or in CI.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #132 will degrade performances by 5.1%

_{Comparing 124-try-and-break-unsafe-usage-in-parameter-extracting (d39ab56) with main (304f5ac)}

Summary

❌ 1 (👁 1) regressions ✅ 15 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	124-try-and-break-unsafe-usage-in-parameter-extracting	Change
👁	path-tree benchmarks/wayfind	55.8 µs	58.8 µs	-5.1%

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 5.66038% with 50 lines in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/errors/path.rs	0.00%	37 Missing :warning:
src/path.rs	22.22%	4 Missing and 3 partials :warning:
src/errors/insert.rs	0.00%	5 Missing :warning:
src/decode.rs	50.00%	1 Missing :warning:

Files with missing lines	Coverage Δ
src/node/delete.rs	77.77% <ø> (ø)
src/node/insert.rs	91.63% <ø> (ø)
src/parts.rs	98.57% <ø> (ø)
src/router.rs	91.83% <ø> (ø)
src/decode.rs	78.12% <50.00%> (ø)
src/errors/insert.rs	76.47% <0.00%> (ø)
src/path.rs	47.36% <22.22%> (-16.27%)	:arrow_down:
src/errors/path.rs	0.00% <0.00%> (ø)